what's your prefered focal? look at your past pictures and get an idea of most used with the 17-40It might be that 17 is the most used - then you might find yourself unhappy with just 21...you get the point

zoom or prime?budget?MF or AF?to use on the FF body?can you rent/borrow it?

For landscapes it's unlikely you'll need a wide aperture (unless you're shooting at night), so a f/1.4 or 2.8 isn't a must. 14L is the widest rectilinear lens Canon makes-- but sometimes I find it a bit too wide, making the composition difficult. the 16-35 is a favorite of many as well if you're wanting to stick with an L lens.

However, is there anything in particular you don't like about your 17-40? I don't know that the 16-35 or even the 14 will be a whole lot wider if that's what you're looking for.

I like 45mm and 90mm for landscapes, so I would probably go with the 45mm and 90mm TS/E. Most people seem to like wider, but I do feel too wide is cheesy. What does the 17-40mm L lack? The 24mm TS/E should be sharper and I find lens movements essential for landscape, but the flexibility of a zoom is nice.

I like 45mm and 90mm for landscapes, so I would probably go with the 45mm and 90mm TS/E. Most people seem to like wider, but I do feel too wide is cheesy. What does the 17-40mm L lack? The 24mm TS/E should be sharper and I find lens movements essential for landscape, but the flexibility of a zoom is nice.

Joaop...If you aren't shooting buildings or other things with straight lines, then the Zeiss 21mm is supposed to be fantastic. I have not tried it, but have tried other Zeiss lenses, such as the 35 and 100 f/2. Be prepared to compensate with a tad of negative exposure comensation, unless you like blown out highlights (you could try HTP, but that's not always the best thing to use). Zeiss glass has a very wide dynamic range. And you probably already know, but the 21mm has "mustache" distortion that is hard or almost impossible to correct. I assume you aren't interested in going wider than 16 or 17mm?

I personally doubt you will prefer the Zeiss 21mm Distagon, over your 17-40L, given the price difference, and the fixed focal length. Sure it will be better, but the results you will get, won't be indicative of the price difference, in my opinion. If the price difference was a bit less, then I would probably say go for it.

If you plan on even doing part of your landscape work in a city, then I would say either the 17 or 24mm tilt-shift lenses would be essential. Also, if you plan on shooting mountains, from a location well below them, in a valley or something...a tilt-shift would come in handy there as well. The same goes for if you are in a high location looking down on something.

You might also consider trying the Rokinon 14mm f/2.8, since the cost is so low. I bought the 85mm 1.4, and it is extremely sharp. Its color and contrast are not "L" quality, but the sharpness is. My copy at least, also has essentially no CA. Of course there is no AF or aperture control via the camera body. I have no idea how the 14mm would compare; I doubt it is as good, and costs more than the 85, but it's a bit less than any other wide angle lens...and certainly a lot less than any f/2.8 wide angle.

Or, if you are open to other longer focal lengths, I can attest that the Zeiss 35mm f/2, is fantastic. I don't know how it compares to the new Sigma 35mm f/1.4 (for the money and the ability to AF, I would certainly buy the Sigma without hesitation...just based on what I have read and seen...and based on my experience with Sigma). But the Zeiss 35mm f/1.4 is supposed to be a tad sharper than the Zeiss f/2. I frankly don't know how you could tell on a (current) Canon full frame body, although you could certainly tell a difference, if there is much of one, on a D800.

I personally plan on getting the Tokina 16-28 f/2.8, because it is optically superior in some aspects, to the 16-35 Canon, yet costs around half the price. I also need f/2.8 for night photography. If I didn't need f/2.8, I would have just been happy with the 17-40L like you have. It is one of the best lens values offered by Canon, or anyone.

I like 45mm and 90mm for landscapes, so I would probably go with the 45mm and 90mm TS/E. Most people seem to like wider, but I do feel too wide is cheesy. What does the 17-40mm L lack? The 24mm TS/E should be sharper and I find lens movements essential for landscape, but the flexibility of a zoom is nice.

I'm weird but I actuall like 100 or 135 .

I do, too, but it's hard to get enough depth of field. Do you ever do focus stacking? I've been thinking about it. Lenses are so close to orthographic when zoomed in that a tilt/shift seems unnecessary if you do focus stacking.

I don't get why landscapes are so often associated with UWA lenses. I prefer much longer lenses for landscapes.

I like 45mm and 90mm for landscapes, so I would probably go with the 45mm and 90mm TS/E. Most people seem to like wider, but I do feel too wide is cheesy. What does the 17-40mm L lack? The 24mm TS/E should be sharper and I find lens movements essential for landscape, but the flexibility of a zoom is nice.

I'm weird but I actuall like 100 or 135 .

I do, too, but it's hard to get enough depth of field. Do you ever do focus stacking? I've been thinking about it. Lenses are so close to orthographic when zoomed in that a tilt/shift seems unnecessary if you do focus stacking.

I don't get why landscapes are so often associated with UWA lenses. I prefer much longer lenses for landscapes.

I agree with you. And no, I don't focus stack yet. Landscape photography is something I haven't really learned to do well yet, but something I'm going to try to learn this spring and summer.